Foldable tire, method and use

Abstract

A collapsible tire for a passenger vehicle, comprising at least one carcass reinforcement optionally associated with an inextensible crown reinforcement, itself radially on the inside of a tread, two beads and two sidewalls, said beads comprising at least one inextensible circumferential reinforcing element called a bead wire, said bead wire defining, when free of any stress, a mean line forming a substantially circular closed curve in a circumferential plane, wherein the invention is characterized in that the bead wire of each bead is flexible, wherein after the tire has been collapsed, the mean line of the bead wire simultaneously defines a first curvature, and a second curvature, the first and second curvatures being connected together by a third connecting curvature, the projection of said first, second and third curvatures of the collapsed tire onto an axial plane defining the two-dimensional envelope by way of a total perimeter P of less than or equal to [3(2H+A)], H being the height of the sidewall and A the width of the tire, and a collapsing method for the tire.

Claims

1. A method for collapsing a collapsible tire, the tire having at least one inextensible crown reinforcement with a thickness of between 2 mm and 7 mm, having a sidewall with a thickness of between 2.6 mm and 7 mm, having a width that is at least 185 mm, and the tire not being mounted on a rim, said method comprising the steps of: simultaneously grasping the tire at a first and a second end of an axis which passes diametrically across the center of the tire, and carrying out, along said axis, a first rotation with a first angle of rotation of the first end and, depending on choice, either carrying out a second rotation with a second angle of rotation of the second end, said first rotation and said second rotation being carried out in opposite directions, or keeping the second end fixed.

2. The method according to claim 1, wherein addition of the absolute values of the first angle and of said possible second angle of rotation results in a value that is between 300 and 360.

3. The method according to claim 1, further comprising applying at least one retaining means to the collapsed tire.

4. The method according to claim 3, wherein the retaining means is applied to the center of the collapsed tire.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention will now be illustrated with the aid of various detailed embodiments that follow and which do not in any way limit the subjects of the invention.

(2) FIG. 1 shows a schematic three-dimensional view of an embodiment of a tire in the uncollapsed state,

(3) FIG. 2 shows a schematic three-dimensional view of a tire which has started to be collapsed, and

(4) FIG. 3 shows a schematic three-dimensional view of a collapsed tire,

(5) FIG. 4 shows a schematic view of a collapsed tire according to FIG. 3 with different axial planes perpendicular to the axis XX, and

(6) FIG. 5 shows a schematic view of the two-dimensional envelope of a collapsed tire according to FIG. 3.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

(7) FIG. 1 shows a passenger vehicle tire, of general reference 1, in the uncollapsed state, comprising a tread 2 extended radially inwards by two sidewalls 3 connected to two beads 4, said beads comprising a bead wire (reinforcing element) (not shown).

(8) Radially on the inside of said tread 2 there are, in succession, an inextensible crown reinforcement (not shown) and a carcass reinforcement (not shown). Each bead 4 has at least one bead wire. This bead wire, which defines a mean line forming a substantially circular closed curve in a circumferential plane, is inextensible and flexible.

(9) The bead wire preferably consists of steel, and is in the form of a saturated and unwrapped cord formed of filaments, said filaments having a diameter equal to 0.18 mm. The cord is a 19.18 metal cord of formula (1+6+12), the layers being formed with the same direction of rotation and with identical pitches equal to 10 mm. Such a cord allows the formation of a bead wire by winding 3 to 16 turns. The number of turns required is dependent on the size of tire and its use.

(10) The mean thickness E.sub.F of the sidewall of the tire according to an embodiment of the invention, measured at the point located in the middle, in the radial direction, between the high point of the bead wire and the low point of the tire on the equatorial plane, is between 2.6 and 7 mm.

(11) The mean thickness E.sub.S of the crown reinforcement 4, measured in the equatorial plane, is between 2 and 7 mm.

(12) FIG. 2 shows a tire, for example of trade reference 185/65 R 14, which has started to be collapsed, and FIG. 3 shows the same tire after it has been collapsed. The tire is collapsed by first of all grasping two ends, comprising a portion of the tread 2 and a portion of the sidewalls 3, said ends being diametrically opposed and located on the axis XX, said axis XX corresponding to the diameter of the tire and thus passing through its centre.

(13) Next, two rotations are carried out, in opposite directions, at these two points about said axis XX. The first rotation has a first angle and the second rotation has a second angle. The result of the addition of the absolute values of the first and second angles is preferably equal to 300.

(14) After collapsing has been carried out, the mean line of the bead wire (reinforcing element) present in the bead 4 then simultaneously defines a first curvature, of general reference 5, defined in the equatorial plane and having a first helix pitch of 61 cm extending anticlockwise in the axial plane, and a second curvature, of general reference 6, defined in the equatorial plane and having a second helix pitch of 65 cm extending clockwise in the axial plane.

(15) As FIG. 4 shows, three axial planes A, B and C have been depicted. The axial planes A and C are disposed more or less at the first curvature 5 and the second curvature 6, respectively, and are perpendicular to the axis XX. The axial plane B, perpendicular to the axis XX, is disposed more or less at the third curvature 7.

(16) The intersection of each of the axial planes A, B and C with the collapsed tire makes it possible to define a two-dimensional envelope of the tire after it has been collapsed according to an embodiment of the invention.

(17) This envelope is defined by projecting onto each axial plane A, B and C the entirety of the impression corresponding to the position of said plane of the collapsed tire. Only all the convex parts relating to the collapsed tire are extracted from these impressions.

(18) FIG. 5 shows the two-dimensional envelope of all of the convex parts extracted and projected onto each axial plane A, B and C of the collapsed tire. As can be seen in this figure, this envelope has an approximately rectangular shape.

(19) The total perimeter of this envelope is obtained by way of the formula:

(20) P<3(2H+A) where A is the width of the tire in the uncollapsed state and H is the height of its sidewall.

(21) Preferably, P<2.5(2H+A).